Nitrogen 1 Flashcards
Where do the plants/animals we eat get their nitrogen?
from nitrogen fixing bacteria - the diazotrophs
What is atmospheric nitrogen fixed to by the nitrogen fixing bacteria?
ammonia
What enzyme does the nitrogen fixing bacteria use?
nitrogenase
What inhibits the activity of the nitrogenase enzyme?
oxygen
What chemical produced by some leguminous plants prevents the inhibition of the nitrogenase enzyme by oxygen?
leghaemoglobin binds to oxygen
How is nitrogen fixed to ammonia by nitrogen fixing bacteria then altered to make it available in a form able to be taken up by plants?
through nitrification, ammonium is converted to nitrite and then to nitrate which is a useable form of nitrogen that can be taken up by plants
Through what amino acid is nitrogen capable of ‘flowing’ through to other biomolecules?
glutamate
Why is glutamate the medium by which other biomolecules receive nitrogen?
it is the only amino acid that is able to obtain its nitrogen directly from NH4 and the only one that is capable of giving up its nitrogen directly
What are the names of the 4 amino acids that are found in much higher concentrations in cells than others?
alanine
glutamine
glutamate
aspartate
What 2 amino acids are excitatory neurotransmitters?
aspartate and glutamate
How do organisms that cannot fix their own nitrogen, preserve the nitrogen that they do have?
by transferring amino groups between different molecules - called transamination
What are 3 general principles of transamination?
- no loss or gain of nitrogen
- readily reversible
- one of the 2 substrate pairs is often glutamate
Describe the functional group structure of an amino acid.
an amino group (NH3+) attached to a carbon that is also attached to an acid group (COO-)
What often reacts with glutamate in transamination?
alpha-ketoacids e.g pyruvate
What are the enzymes that are involved in transamination?
aminotransferases
What do aminotransferases rely on for their activity?
pyridoxal phosphate cofactor
What molecule typically accepts amino groups?
alpha-ketoglutarate (in reverse reaction)
What vitamin is pyridoxal phosphate cofactor made from?
vitamin B6
What does the pyridoxal phosphate cofactor do during transamination?
transfers the amino group
What is the diagnostic value of plasma aminotransferases?
they are intracellular enzymes and so being outside the cell in plasma indicates cell damage
What are the 3 circumstances of amino acid oxidative catabolism?
- leftover amino acids from normal protein turn over are broken down
- too many amino acids obtained from diet that we don’t need
- when carbohydrates are in short supply
How are dietary proteins metabolised?
they are enzymatically hydrolysed
What does pepsin do?
it cuts protein into peptides in the STOMACH
What do trypsin and chymotrypsin do?
cut proteins and larger peptides into smaller peptides in the SMALL INTESTINE
What do Aminopeptidase and carboxypeptidases A and B do?
degrade peptides into amino acids in SMALL INTESTINE
What is the end point of dietary protein degradation?
individual amino acids
Why must protein ingested that is surplus to the body’s requirements be catabolised?
there is no storage facility for excess protein
